Messages in this thread | | | Subject | Re: [PATCH] platform: finally disallow IRQ0 in platform_get_irq() and its ilk | From | Sergey Shtylyov <> | Date | Thu, 9 Dec 2021 23:21:41 +0300 |
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On 12/9/21 11:06 PM, Andy Shevchenko wrote:
>> The commit a85a6c86c25b ("driver core: platform: Clarify that IRQ 0 is >> invalid") only calls WARN() when IRQ0 is about to be returned, however >> using IRQ0 is considered invalid (according to Linus) outside the arch/ >> code where it's used by the i8253 drivers. Many driver subsystems treat >> 0 specially (e.g. as an indication of the polling mode by libata), so >> the users of platform_get_irq[_byname]() in them would have to filter >> out IRQ0 explicitly and this (quite obviously) doesn't scale... >> Let's finally get this straight and return -EINVAL instead of IRQ0! > > You are changing the return value of platform_get_irq_optional(). > The problem here is the proposed change doesn't bring any value in such > case. platform_get_irq_optional() should be able (at the end of the day) > to return 3 types of values (as other APIs do): > > 0: success > == 0: IRQ not found > < 0: an error that must be consumed by the caller
I remember that was in your patch that got reverted right after being merged. ;-) IMHO returning both error code and 0 on failure is a sign of a misdesigned API, it makes the failure check unnecessarily complex and error prone.
> 0 is unexpected result for non-optional APIs and there you may try to play > tricks (like replacing it by error code). > > There was a discussion around the topic: > https://lore.kernel.org/lkml/20210331144526.19439-1-andriy.shevchenko@linux.intel.com/T/#u
I don't see much of the discussion there...
> Wanna help?
No, I'm afraid you're on your own here...
>> Fixes: a85a6c86c25b ("driver core: platform: Clarify that IRQ 0 is invalid") > > Not sure.
Why? It fixes gthe IRQ0 problem, so that you don't have to check for IRQ0 in many callers (for the subsytems that treat 0 as s/th special, like polling mode)... If you have something to improve, you can do that atop of this patch...
MBR, Sergey
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